Compound-specific δ2H and δ13C values of n-alkanes as a tool to unravel complex petroleum mixtures in the South Viking Graben, Norway. (February 2021)

• Record Type: Journal Article
• Authors: Murillo, Wendy A.; Horsfield, Brian; Garcin, Yannick; Vieth, Andrea; Sachse, Dirk
• Is Part Of: Organic geochemistry. Volume 152(2021)
• Publication Date: 2021-02
• Subjects: Norwegian North Sea -- South Viking Graben -- Petroleum mixtures -- Compound-specific stable carbon and hydrogen isotope compositions -- Normal Alkanes -- Acyclic isoprenoid alkanes -- Oil-source correlation -- Unraveling oil mixtures -- Thermal maturation -- Hydrogen exchange; Organic geochemistry -- Periodicals; Biogeochemistry -- Periodicals; Géochimie organique -- Périodiques; 553.205
• DOI: 10.1016/j.orggeochem.2020.104167
• Languages: English
• ISSNs: 0146-6380

Abstract

Highlights: δ 2 H values of alkanes proved to be a useful tool to discriminate petroleum mixtures. n -Alkanes (>C20 ) showed a higher 2 H-enrichment with the input from terrigenous source material to oil mixtures. Combination of δ 13 C and δ 2 H values of n -alkanes provided an improved resolution to unravel petroleum mixtures. δ 2 H values of n -alkanes from source rock extracts were mainly controlled by the δ 2 H of biosynthetic precursors. Abstract: In order to resolve oil mixtures and for oil-source correlation purposes, both hydrogen (δ 2 H) and carbon isotope compositions (δ 13 C) of n -alkanes and acyclic isoprenoid alkanes have been determined in petroleum mixtures and extracts from Jurassic source rocks of distinct organic matter type, depositional setting and lithology in the South Viking Graben, Norway. δ 2 H values vary from −80 to −140‰ for n -alkanes and from −130 to −165‰ for pristane (Pr) and phytane (Ph) in oil and condensate samples. At the same maturity level, in the main oil generative window, individual n -alkanes from most oils and condensates show a 2 H-enrichment with n -alkane chain length by 15 to 50‰. With the increase in the estimated input of hydrocarbons from terrigenous source material to petroleum mixtures, the n -alkanes (>C20 ) exhibit a higher 2 H-enrichment while n -alkanes (C10 -C14 ) show a higher 13 C-enrichment. δ 2 H values of n -alkanes (>C20 ) are useful to discriminate mixed oils that were not well differentiated by δ 13 C data. δ 2 H values of individual n -alkanes from oils suggest a possible exchange of C-bound H with other hydrogen during their generation from precursor molecules. We find that δ 2 H values of n -alkanes from Jurassic source rock extracts, at the onset of oil generation, were mainly controlled by the isotopic composition of biosynthetic precursors and varied from −100 to −150‰. Combination of carbon and hydrogen isotope compositions of n -alkanes proved to be a useful tool to discriminate Jurassic petroleum mixtures from distinct sources in the Norwegian South Viking Graben.